addNameValue nm val req augments the request req with a binding
for (nm,val). Neither nm nor val are assumed encoded. It leaves it
until the serialization phase to fix on how to communicate the binding
for the POST request (i.e., via the query portion or in the request's body.)

addQueryNameValue nm val req performs same function as addNameValue,
but adds the constraint that the binding must be transmitted as part of the
body of the POST request, forcing the payload to be of MIME type application/x-www-form-urlencoded